True story: a CMM Level 5 software organization had precisely the exact same issue. There was a PM, who would literally spend the entire day wasting time and start real work around 5 PM. Then work till late night.

Once he advised me, "Always make sure that you send an e-mail, late at night to anybody in the organization, before you call it day."

"Why?"

To make it short, per his advise, the single most important thing about those e-mails, wasn't the contents, but just the timestamp.